The present invention relates generally to video systems and more particularly to a video conversion system for converting interlaced images to progressive images.
Currently the majority of video signals are formatted according to the National Television Standard Committee (NTSC) standard. A NTSC video frame typically consists of two fields, each field containing alternating frame lines. The two fields are scanned independently 1/60 seconds apart and interlaced to produce a video frame. Referring to FIG. 1, shows a moving object at a position 110 representative of an object in field 1 scanned in at time t.sub.1. Position 112 is representative of the same object in field 2 scanned in at time t.sub.2.
NTSC standard video signals, which are interlace scanned to reduce the signal bandwidth, provides satisfactory motion rendition. The interlaced video format, however, is not well suited for a number of applications related to video compression and still-image hardcopy and display. For example, video compression algorithms such as MPEG-1 assume the video input to be progressive which decreases the coded image quality of interlaced videos. As for still image hardcopy and display, interlaced images introduce visually annoying artifacts that appear as serrated edges in motion regions. Referring to FIG. 2 shows a representation of the moving object of FIG. 1 stored in a non-interlaced progressive format. The motion which occurs between the scanning of object between field 1 and field 2 of the video frame results in the serrated edges shown in FIG. 2.
Converting interlaced video sequences to progressive format, simply known as deinterlacing, is an important technique for processing digital videos from NTSC sources. Deinterlacing algorithms that convert interlaced sequences to progressive sequences typically follow two approaches. The first approach uses information from only one of the fields and interpolates the video input information to full frame. Although this approach typically only requires two field buffers it does not detect inter-field motion and typically results in blurring of the video image since half of the video input information is discarded. The second deinterlacing approach uses information from both fields to construct the progressive frame. Although this approach has the potential of producing a better image quality, it is at the expense of increased computational complexity and/or increased buffer requirements as this approach typically requires using three field buffers.
A video conversion system for converting interlaced images to progressive images which produces high quality images without high computational complexity and/or buffer requirements is needed.